Reading in Matthew 26 we see a woman coming into the room where Jesus is about to eat, she then begins poring expensive perfume over him; and yet, while in the next scene we see Judas Iscariot selling information about where Jesus will be, so that those who want to kill him can be waiting for him. One person (the woman with expensive perfume) is giving without cost because her heart is filled with gratitude, while the other person, (Judas) is looking for gain only for himself.
I find that it is an easy lesson to learn, but sometimes hard to do. That is, in putting my selfish desires behind me. At times, when my heart is looking at only gain for myself, I need to pray and ask God first for forgiveness, and then to ask him to change my heart. Satan wants us to think only of ourselves, thinking nothing of how it might benefit or hurt others.
Sometimes what I need most is the strength just to surrender in what "I" want to do, think or have. In my mind I can justify a thousand different reasons why I deserve or should have my own way. Then the Holy Spirit pulls on my heartstrings and I know what I must do, surrender my will to that of our Lord's. Sometimes it is not easy, but when I ask him, Jesus gives me the strength to relinquish what truly is not mine to keep. "Lord, I don't want to give this to you, but give me the strength and the desire to do 'your' will concerning this." When giving my desires to him, he then can give me peace, and more importantly, contentment.